\begin{abstract}
The paper presents a library for Julia---new 
scientific programming language. The library implements embedded 
Runge-Kutta methods with step control. the creation of new library is 
a reasonable step because of the novelty of language and requirement to be able to
easily add new methods by specifying their coefficients tables. 
Purpose of this work is the description of  
embedded Runge-Kutta methods implementation and it's application to 
``competitor-competitor-mutualist'' biological model. 
For the solution of a system of ordinary
differential equations this model uses embedded Runge--Kutta methods
of high order with step control.
Results of numerical analysis of the model are
consistent with analytical research.
Our library allows to use Julia language for
numerical solution of ordinary differential equations by high order
methods and to test selected methods for adequacy to a specific
problem.
\keywords{numerical simulation, biological models, 
  embedded Runge--Kutta methods, Julia programming language}
\end{abstract}
